An air compressor is an incredibly use tool. You can use it to power a nail gun or a paint sprayer. It can be used to pump up your car or bicycle tyres. You can fill up gas cylinders with one. It can be used to power pneumatic tools like a jackhammer. You want to buy the best air compressor for you. This will depend on what you need it for. There are many types of air compressors so you should choose the one that matches what you want to do with it.
You can get a gas powered air compressor or an electric air compressor. There are ones designed for use at home or maybe you need industrial air compressor if you need it for work. Maybe you need to use it in many different locations so you should get a small portable air compressor. The point is that you should think about how you will use the air compressor before making your buying decision.
Air Compressor Types
There are many different styles of air compressors. You choice will depend on your particular needs. Different tank styles are good for different applications. The size and position of the tank can affect the stability of the machine and the amount of space it takes up.
Hot Dog Compressors
Hot dog compressors have a cylinder shaped tanks. The tanks is usually below the motor. They are popular for most DIY enthusiasts. They are powerful enough to power smaller air tools like brushes and staples. They are relatively low-maintenance.
They tend to be heavier than pancake compressors. If you get one of these think about how you will move it around. Many of them come with a handle. They can be quite noisy.
Pancake Air Compressors
Pancake compressors come with a round flat storage tank that sits below the motor. This design is the most stable. The tank volume can range from 1 to 6 gallons.
They don’t require too much maintenance. They are good for using with small air tools. They don’t have the capacity to deal with heavy duty tools.
Twin-Stack Air Compressors
Twin-stack compressors are very like hot dog compressors. Rather than one tank they have two horizontal cylinder tanks positioned on top of each other.
The two tanks gives the twin-stack design a larger capacity which means they can power a nail or brad gun. Due to the two tanks the twin-stack can be quite heavy but it is still portable.
Pontoon Air Compressors
Pontoon air compressors are like twin-stack compressors. They have two cylinder tanks but they are positioned on either side of the unit like a pontoon boat. It functions in the same way as the twin-stack air compressors.
Wheelbarrow Air Compressors
Wheelbarrow air compressors also have two cylinder tanks positioned horizontally. They have handles at the back like a wheelbarrow with wheels that allow you to move it around like a wheelbarrow. The often have powerful motors and can be quite heavy.
Vertical and Horizontal Compressors
If you are short of space an air compressor with vertical tank will take up less space. The problem with vertical tanks is that they are less stable than horizontal ones. If you are short of space and you don’t need to move your compressor around much a vertical compressor is ideal. It is possible to buy both portable and stationary compressors that have either vertical or horizontal tanks.
Portable Air Compressors
Portable compressors come in a variety of styles described above. Portable air compressors usually have a handle and/or wheels. They are versatile and very popular with both DIY enthusiasts and professionals.
Stationary Air Compressor
Stationary air compressors cannot be moved around easily. This is an industrial air compressor. They are designed to stay in one location due to their size and weight. Their tanks are larger. They can be used with all air tools. These are ideal if you are a professional with a workshop or garage.
They generally have a two stage compressor type with twin pistons that produce a large amount of pressure. They produce high CFM (cubic feet of air per minute) rates. The large storage tanks allow them to be used for a long time without interruption.
Vehicle-Mounted Air Compressors
Vehicle-Mounted Compressors are large and powerful compressors that are fitted to the back of a truck. If you need a large amount of power that can tackle any job and you also need to move it around a truck mounted compressor is the answer. Some vehicle mounted compressors work off your engine while others use hydraulics.
Inflators are the smallest kind of air compressors. Inflators don’t have a storage tank. This is why they are much smaller. It runs continuously providing pressurised air. It does not store the air in a tank. Inflators can be used for inflating small boats, tyres and sports equipment.
Electric or Gas Powered Air Compressors
Choosing the type of power source for your air compressor is important. The choice is between electric air compressors and gas air compressors. Electric air compressors plug into the wall. They do not run on batteries. Gas air compressors requires gasoline to run.
Typically electric air compressors are quieter than gas air compressors as gas compressors have a internal combustion engine attached to them. Electric air compressors require less maintenance. Electric compressors are convenient when you have easy access to a power supply. You don’t need to worry about bringing fuel. With a gas model you will need an adequate supply of gasoline whenever you use it.
Most portable can operate on standard household voltages. If you want to use an electric air compressor you must be near to an electric socket. Obviously this limits where you can use an electric air compressor. For this reason gas air compressors are better if you intend to use them outdoors. You can use it anywhere you can move the compressor along with a can of gas.
Gas compressors tend to have more horse power meaning that they have higher PSI. Therefore they can be more suitable for heavy duty uses and high powered air tools.
Gas Air Compressor Pros
- Use anywhere
- Higher HP, PSI and CFM
Gas Air Compressor Cons
- Generally noisier
- More maintenance required
- Need to carry fuel
Electric Air Compressor Pros
- Less maintenance required
- No need to carry fuel
Electric Air Compressor Cons
- Lower HP, PSI and CFM
- Need to be near an electric socket
Air Compressor Terminology
PSI or pounds per square inch is a measure of pressure. Most compressors produce enough pressure to work DIY tools. The higher the pressure the more air that can be stored in the same tank. A one gallon tank at 200 psi can hold as much air as a 2 gallon tank at 100 psi. The more air you have in the tank the longer you can use the compressor for without interruption.
CFM (cubic feet per minute) tells you how much air a compressor can provide in a minute. This is a very important figure to consider. Different air tools use air at different rates. If your tool uses air at a faster rate than your air compressor can provide it you will have to pause and wait for the compressor to fill the tank again. CFM is generally measured by the manufacturer at a pressure of 90 psi so it is a good measurement to use when comparing different air compressors. You can be sure you are comparing like with like.
Horsepower (HP) is the power produced by the air compressor’s engine or motor. Generally the higher the horsepower the faster the recovery time for the compressor will be. The more powerful the engine or motor the faster it will be at filling the tank with pressurised air.
It is more important to look at the PSI and CFM. These specifications will tell you if your compressor is powerful enough to use with particular air tools.
Tanks size can be important. The larger the tank the more air it can store. Therefore with a larger tank you will be able to use the compressor for longer without interruption. With a smaller tank you may find that the pressure drops and the motor kicks in. So if you intend to use your compressor for applications that demand sustained air pressure for long periods of time a larger tank is needed.
The dBA is a measure of how loud the compressor is. The quieter the unit is the better for a variety of reasons. Firstly you don’t want to damage your hearing. Secondly you don’t want to disturb the people near you. If you are a DIY enthusiast you don’t want to disturb your family. Likewise if you are a professional the quieter the air compressor the happier your clients are likely to be. If you can avoid upsetting your client and their neighbours you will have higher customer satisfaction.
When choosing an air compressor check the dBA specification on the unit. It is a good idea to look at videos of the unit in action. From this you can get a good idea of the type of noise it makes. It may have a particularly annoying sound at a relatively low dBA.
Currently it is not possible to have an air compressor that produces no noise. You may have to make a trade off between noise and power. Try to find a unit that balances power and noise. You want an air compressor that is powerful enough to meet your requirements and quiet enough to not overly disturb people around it.
The weight of an air compressor is an important factor in your buying decision. Larger compressors are heavier and harder to move around. At the same time larger compressors have bigger tanks and more power. The decision really depends on how you intend to user your compressor. If you intend to use it in a variety of locations and you need to transport it frequently a smaller lighter compressor is the way to go. However the compressor needs to be up to the jobs you use it for. A smaller compressor won’t have the power needed for continuous use over long periods of time as it will need more refill time.
A top range smaller air compressor will have many of the features of the larger units. If you are unsure of what to go for a smaller unit will be more versatile. Ultimately it comes down to how you intend to use the unit. Don’t choose a smaller unit if you are sure it won’t be up to the job.
Air Compressor Technology Types
There are three major types of air compressor technologies. They are reciprocating, rotary screw and centrifugal. They all are described below. In addition to these three main types there are variations specified by:
- Lubrication – oil or oil-free where no oil contacts the compressed air
- Cooling method – air, water or oil
- Drive method – motor, engine, steam
- The number of compression stages
Reciprocating Air Compressors
A reciprocating air compressor or piston air compressor is a positive-displacement compressor that uses pistons driven by a crankshaft to deliver air at high pressure. Positive-displacement means that the pressure of the air is increased by decreasing the volume.
The gas flows into the compression cylinder where it is compressed by a piston that is moved back and forth by a crankshaft (reciprocating motion) and then discharged.
There are single stage and two stage compressors. Two stage compressors are used for higher pressures.
There are single acting compressors and double acting compressors. A double acting compressor uses both sides of the piston. They can be air or water cooled and oil or oil-free.
Rotary Screw Compressors
A rotary screw compressor uses a rotary type positive-displacement mechanism. The air compression process uses two meshing helical screws called rotors to compress the gas. Air enters at one side of the rotors and passes through the threads of the rotors as they rotate. These meshing rotors force the gas through the compressor where it exits at the end of the screws.
The air compression process of a rotary screw is continuous meaning there is little pulsation or surging of flow which occurs with reciprocating air compressors.
Rotary screw compressors are relatively easy to maintain and use. They can be air cooled or water cooled and oil or oil-free.
Centrifugal air compressors are also known as radial air compressors. They work by the transfer of energy from a rotating impeller to the air. This type of compressor converts angular momentum from the spinning impeller into pressurised air. Centrifugal compressors rotate at a higher rate than other types of compressors. The flow of air through the compressor is continuous.
Centrifugal compressors are oil-free. Any lubrication of the motor and drive shaft is isolated from the impeller and the air that passes through it.
Frequently Asked Questions
Here are some examples of what CFM is needed various tools. The following figures are based on a pressure of 90 psi with the tools running 25% of the time. These are only examples. Different tools will vary so be sure to check you tool’s manual for accurate figures.
0.5 CFM – Brad Nailer
1 CFM – Compression Riveter, Tire Changer
2 CFM – Pneumatic doors, Tire Inflation, Valve Grinders
3 CFM – Blow Gun, Pneumatic Garage Door, 1/4″ Ratchet
4 CFM – Brake Tester, Air Hammer, Caulking Gun
5 CFM – Bench Rammer, Speed Saw, Spark plug cleaner
6 CFM – Bus Lift, Hydraulic Floor Jack, Jitterbug Sander
7 CFM – Floor Rammer, 3/4″ Impact Driver
8 CFM – High Speed Grinder
10 CFM – Lift, Bus or Truck, Large Rammers
12 CFM – Bead Breaker, 8 Inch Circle Saw
20 CFM – Paint Sprayers, Air Bushing
22 CFM – Heavy Air Hammer
100 CFM – Rock Drill
135 CFM – Medium Jackhammer
Oil or Oil-free?
Most small air compressors are oil-free. This means that you don’t have to check or change the oil. However oil lubricated models will generally last longer than oil-free compressors do. With normal DIY usage having an oil-free air compressor shouldn’t be a problem.
How to Choose a Home Based Air Compressors?
If you plan to use your air compressor around the home your primary concern is probably noise. You should look for a unit with a low dBA. So you should avoid the very large and powerful units. Going for a smaller unit is advisable. As you are only using it in the location of the home you can go for a small unit with a large tank. Portability isn’t the biggest concern. A large tank means you can use the air compressor for longer without interruption.
If you have a large property and plan to use the compressor then portability might be more of an issue. Similarly if you want to use the unit in your garage you might have more heavy duty applications for it and a more powerful unit might be in order.
Typically for a home low dBA is important while a large tank will give you a wider range of uses at the expense of portability.
How to Choose a Work Based Air Compressors?
If you are working in a small team you need a unit that can handle multiple users. You don’t really want a portable unit unless you want to get one for each person in the team. So a large unit that several people can connect to would be more practical. If you have a large team it would be a good idea to have a couple of portable air compressors as a back up and for use in tight or awkward spaces.
If you are a contractor working on your own you should probably look at getting a portable air compressor with a large tank. This would be important if you are moving around a lot or going up on roofs. You want something portable. However if you are going to be on the ground all the time a large compressor that can maintain power might be more suitable.
How to Choose a Portable Air Compressors?
A modern portable air compressor is a great thing to have in your set of tools. These compressors now have good PSI levels. They give you a good balance between recharging and working.
The weight of these units mean they are easy to carry between floors. Not only are they portable, they are easy to store too. This can be an important consideration if you have a small vehicle or live in an apartment.
Unless you want extreme portability you should avoid getting tankless inflator. These can be very useful for small jobs but a tank is important if you are doing sustained work.
Large vs Small – Power vs Portability
Size and portability are important considerations when buying your air compressor. Portable compressors come in different sizes and shapes. They are small and easy to move around. The large compressors have more power. Some large compressors will have wheels that help when moving them around.
If you only have light applications for your compressor like powering nail cus and inflating tyres you should go for an oil-free compressor with a tank that can hold 2-6 gallons. If you have more demanding applications than a bigger tank will be needed.
Stationary compressors cannot be move around easily. You generally keep it in one place in your workshop. Their tanks can hold 60 to 80 gallons and they will have higher horsepower motors. They are usually powered by electricity. If you have heavy applications and you do all your work in one garage or workshop then you should think about a stationary compressor.